1. Field of the Invention
The present invention relates to a microelectronic battery and more particularly to a microelectronic battery formed as a volume energy storage device from soft lithography techniques which provides increased capacity relative to so-called thin film batteries or area energy storage devices.
2. Description of the Prior Art
Thin film microelectronic batteries are known. Examples of such batteries are disclosed in U.S. Pat. Nos. 5,338,625 and 5,567,210. Such thin film batteries are formed by depositing an anode, such as vanadium on a substrate. A cathode, such as amorphous vanadium oxide, VOx, is deposited on a portion of the anode. An amorphous oxynitride lithium electrolyte film is deposited on top of the cathode to form a Li—VOx battery cell.
The footprint of the Li—VOx battery cell is about one square centimeter and about 8 microns thick. Such a configuration provides about 130 microamp hours of battery capacity. In order to increase the capacity of such a thin film battery, the area dimensions are increased. As such, such thin film batteries are known as area energy storage devices.
Unfortunately, applications exist in which the area or footprint is limited and increased capacity is required. Examples of such applications include high speed electronics applications and certain military applications. In particular, high speed electronics applications are known in which the processing speed is so fast that on-chip/on-board power supplies are required to prevent local current starvation. Military applications are also known with space constraints and relatively high capacity requirements. Examples of such military applications include sensor applications used in covert applications. Due to the capacity or requirements and space limitations, thin film power supplies are unsuitable.
In order to increase the battery capacity for use in such applications without increasing the footprint, one possible solution is to utilize a different battery technology which provides a higher capacity. For example, Zn/Air batteries are known to have the highest volumetric energy storage (36 J/mm3) of any known battery technology. In addition to having a high capacity, Zn/Air batteries provide other advantages. For example, Zn/Air batteries are also known to have a relatively flat discharge curve with a relatively long storage life. Moreover, such Zn/Air batteries have already been demonstrated to be environmentally safe and are amenable for use in medical applications. Examples of such Zn/Air batteries are disclosed in U.S. Pat. Nos. Des. 427,144 and 4,842,963.
Unfortunately, such Zn/Air batteries have heretofore only been known to be formed on a macroscale, thus making them unsuitable for use in various microelectronic applications as discussed above. Thus, there is a need for a microelectronic battery having increased capacity relative to known thin film batteries for use in applications which require relatively high capacity in a relatively small area or footprint.